Pandora wrote:
I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

Without a battery, I'm not sure how to test whether or not the charger
is working properly. The green "charged" LED lights up when the 2V or
4V range is selected, even though there is nothing across the output
terminals. Measuring the o/c d.c. voltage and s/c current across the
output terminals gives readings of a few hundred millivolts and
microamps.

I looked inside the charger and there is no sign of overheating
anywhere.

At the a.c. power supply input, there is a step-down mains transformer
and some large electrolytics and several rectifier diodes. On the
p.c.b., there is one LM339N quad comparator (which has a voltage of
7.6V between its supply pins 3 and 11). A TIP3055 power transistor on
a large heatsink is also present and a few small signal transistors.
Other than that I can only see resistors and a few small signal diodes
and zeners.

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

Thanks folks.


If it says it is a 1A charger then a 1 Ohm 5W resistor should cause it
to click. The charger may turn off on undervoltage thinking you have a
shorted cell. In that case put 2x 1 ohms in parallel and then put that
combo in series with the 1 Ohm for 1.5 Ohm total, it should start
charging that. Clip your VOM across the total load, plug the charger in,
and be ready to unplug if the voltage is much greater than 1.5V.